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GA-NIFS: Multi-phase outflows in a star-forming galaxy at
No full textInternational audienceGalactic outflows driven by star formation or active galactic nuclei are typically formed by multi-phase gas whose temperature spans over 4 orders of magnitude. Probing the different outflow components requires multi-wavelength observations and long exposure times, especially in the distant Universe. So far, most of the high-z studies have focused on a single gas phase, but this kind of analysis may potentially miss a non-negligible fraction of the total outflowing gas content. In this work, we analyze the spatially resolved rest-frame UV and optical emission from HZ4, the highest redshift main sequence star-forming galaxy having a detected [C II] outflow, which traces the neutral gas component. Our goal is to study the ionized interstellar medium in the galaxy and the properties of the ionized outflow as traced by the [O III]5007Å and H emission lines. We exploit JWST/NIRSpec observations in the integral field spectroscopy mode to investigate the galaxy properties by making use of the brightest rest-frame optical emission lines. Their high spectral and spatial resolution allows us to trace the ionized outflow from broad line wings and spatially resolve it. We also re-analyze the [C II] ALMA data to compare the neutral atomic and ionized outflow morphologies, masses, and energetics. We find that the system consists of a galaxy merger, instead of a rotating disk as originally inferred from low-resolution [C II] observations, and hosts an extended ionized outflow. The ionized outflow is being launched from a region hosting an intense burst of star formation and extends over 4 kpc from the launch site. The neutral and ionized outflows are almost co-spatial, but the mass loading factor in the ionized gas phase is two orders of magnitude smaller than in the neutral phase, as found for other lower redshift multi-phase outflows
Geomorphological signatures of known climatic extreme events and validation of theoritical emplacement approach: Boulders on Cuban low-lying Marine Terraces
No full textInternational audienceTo assess coastal hazard where Coastal boulder deposits (CBDs) are found, it is crucial to constrain the forces governing their emplacement: from either storms/tropical cyclones or tsunamis. Here we focus on the CBDs on the island of Cuba and the extreme climatic events responsible for their formation. Four sites are being studied to identify the CBDs produced during known hurricanes over the last fifty years.The selected CBDs are located on a low-lying coral reef terrace on the Cuban shore, emplaced by the Cuban hurricane of 1935, Lili hurricane of 1996 and Matthew hurricane of 2016. These meteorological events associated with reported geomorphological objects are analyzed to quantify the hydrodynamic parameters of such extreme events (maximum orbital velocity). Furthermore, the quantification of CBDs volume by stereophotogrammetry (using Agisoft Metashape Professional version 1.7.2) and CBDs density by water immersion method on samples allow us to use deterministic and theoretical approaches ( hydrodynamics equations of Nandasena et al., 2013, 2022 ) to assess the assumed associated hydrodynamic parameters (minimum flow velocity) responsible for the dislocation of the coral reef terraces and transport of the resulted boulders. Finally, we compare these velocities with ones calculated from the meteorological events to discuss the reliability of these approaches to determine the climatic or tsunamigenic origin of the past extreme waves from geomorphological analyses of CBDs
Evolutionary tracks, ejecta, and ionizing photons from intermediate-mass to very massive stars with PARSEC
No full textInternational audienceRecent advancements in stellar evolution modeling offer unprecedented accuracy in predicting the evolution and deaths of stars. We present new stellar evolutionary models computed with the updated PARSEC V2.0 code for a comprehensive and homogeneous grid of metallicities and initial masses. Nuclear reaction networks, mass loss prescriptions, and the treatment of elemental mixing have all been updated in PARSEC V2.0. We computed models for thirteen initial metallicities spanning to , with masses ranging from 2.0 M to 2000 M, consisting of a library of over 1,100 ( tracks including pure-He models) full stellar evolution tracks. For each track, the evolution is followed from the pre-main-sequence to the most advanced early-asymptotic-giant-branch or the pre-supernova phases, depending on the stellar mass. Here, we describe the properties of the tracks and their chemical and structural evolution. We computed the final fates and the remnant masses and built the mass spectrum for each metallicity, finding that the combined black hole (BH) pair-instability mass gap spans just between 100 and 130 M. Moreover, the remnant masses provide models consistent with observed BH masses, such as those from the primaries of GW190521, Cygnus X-1, and BH3 binary systems. We computed and provided the chemical ejecta from stellar winds and explosive final fates, along with the ionizing photon rates. Our results show strong overall consistency with other tracks computed with different codes. A comparison with a large sample of observed massive stars in the Tarantula Nebula of the Large Magellanic Cloud shows that our tracks nicely reproduce the majority of stars that lie on the main sequence. All the models are publicly available and can be retrieved on the PARSEC database
"Groundbreaking study: Combined effect of marine heatwaves and polyethylene microplastics on Pacific oysters, Crassostrea gigas"
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Magnetometry: Solving the fundamental ambiguity from line pair inversion
No full textInternational audienceContext. All magnetic field vector measurements lead to ambiguous results. Aims. We demonstrate that carrying out observations in two different lines belonging to the same multiplet, but with different absorption coefficients (and thus formed at two different depths, e.g., Fe I 6302.5 Å and 6301.5 Å) allow for the azimuth ambiguity remaining from the Zeeman signal interpretation to be resolved. Methods. The measurement based on an interpretation of the Zeeman effect relates to the magnetic field, H, and not the divergencefree magnetic induction, B. We analyzed how the anisotropy of the photosphere, which is strongly stratified due to gravity and density at the star surface, affects the estimation of div H. We also considered how the ambiguity resolution ought to be performed in these conditions. Results. We obtained two ambiguity-resolved field vector maps at two different, but nonetheless close altitudes. This allowed us to derive the current density full vector via curl H = J. The process revealed the horizontal component of the current density, which is generally found to be markedly larger than the better known vertical one. We observed some systematical trends and present some examples in this paper, such as circular currents wrapping spots clockwise about a positive polarity spot and counterclockwise about a negative polarity spot. We also detail the strong horizontal current components crossing active region neutral lines. Conclusions. Finally, we remark that the Na I D1 and D2 lines form another such line pair. We propose them as a way to access the low chromosphere where they are formed. However, a better spatial resolution for both observations and analysis would likely be necessary in such a medium.</div
Accurate estimation of photosynthetic available radiation from multispectral downwelling irradiance profiles
No full textInternational audienceAbstract Photosynthetic available radiation (PAR) is the light usable by photosynthetic organisms. Photosynthetic available radiation measurements at depth are required to quantify the light availability for primary production. Direct PAR measurements may be measured with full‐spectrum quantum sensors for the range 400 to 700 nm. When spectrally resolved light is measured, as for the downwelling irradiance spectrum , PAR may be computed by numerically integrating within those limits. As radiation varies across a spectral continuum, needs to be resolved at a sufficiently large number of bands, to provide an unbiased PAR estimate. When is available at a small number of spectral bands, as for multispectral sensors, it is still possible to numerically integrate , but the estimation will contain errors. Here, we propose a method that delivers unbiased PAR estimates, based on two‐layer neural networks, formulable in a small number of matrix equations, and thus exportable to any software platform. The method was calibrated with a dataset of hyperspectral acquired by new types of BioGeoChemical (BGC)‐Argo floats deployed in a variety of open ocean locations, representative of a wide range of bio‐optical properties. This procedure was repeated for several band configurations, including those existing on multispectral radiometers presently the standard for the BGC‐Argo fleet. Validation results against independent data were highly satisfactory, displaying minimal uncertainties across a wide PAR range, with the performance varying as a function of each sensor configuration, overall supporting the operational implementation in the Argo program. Model codes are findable at https://github.com/jaipipor/PAR_BGC_Argo
Counter-intuitive links between cave genesis and subaerial stream dynamics in the Têt valley–Lachambre network, eastern Pyrénées, France
No full textInternational audienceThe Lachambre cave network (Eastern Pyrenees, France) is well suited to studying the interaction between vertical successions of low-gradient cave passages in the limestone and chronosequences of fluvial terraces in the adjacent valley. Investigations here focus on cave passages striking parallel to the Têt River, and on their topographic, geomorphological, sedimentological and geochronological relationship with the two youngest generations of Pleistocene fluvial terrace, T2 and T1. Results reveal that the longitudinal profiles of the terraces and modern thalweg (1.5–3%) are ten times steeper than the profiles of the subterranean passages (0.1–0.3%), which display typical characteristics of water table caves. The respective cave and fluvial terrace profiles consequently diverge scissor-like on either side of a point of intersection, with the elevation of cave levels upstream occurring below the elevation of comparatively younger terrace treads, and even below the modern thalweg. U/Th ages obtained from speleothems and previously published 26Al/10Be burial ages of quartz-rich sediment indicate that the downstream segment of the cave passage (i) formed during Marine Isotope Stage 6, (ii) was invaded soon after by a subterranean debris cone (at times of fluvial aggradation in the Têt catchment, cones of river bedload entered the caves through valleyside sinkholes), (iii) was partially filled by an influx of gravel from upstream during MIS 4, (iv) experienced speleothem growth during MIS 3, and (v) underwent further geomorphic changes during MIS 2. Such complicated interactions between subaerial and subterranean dynamics emphasize the necessity for caution when using caves as tools for quantifying valley incision by rivers – particularly when using them as substitutes for fluvial terraces in widespread situations where none are available. Cave altimetry, speleogen inventories, cross-cutting relations in cave sediment stratigraphy and age-bracketing of fluvial deposits and speleothems all contribute to elaborating a more accurate understanding of how cave development interrelates with Quaternary alluvial cycles
The Land Surface Interactions with the Atmosphere over the Iberian Semi-Arid Environment (LIAISE) field campaign
No full textInternational audienceOne of the greatest challenges facing environmental science is to better understand the impacts of predicted future changes in the terrestrial hydrological cycle. It has been recognized that human activities play a key role and must therefore be considered in future climate simulations. The representation of anthropization in land surface schemes within global earth system models is at a relatively nascent stage and must be improved for more accurate future projections of water resources. The understanding of the impact of anthropogenic processes has been hampered by the lack of consistent and extensive observations. Here, we present the Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment (LIAISE) project field campaign which brought together ground-based (surface energy budget estimated at 7 sites, 269 radio soundings made at 2 sites and multiple remote sensing instruments for profiling the lower atmosphere), airborne measurements (3 airplanes and numerous drones measuring surface and atmospheric properties) and satellite data (to derive estimates of irrigation timing, soil moisture, evapotranspiration and surfacetemperature) to improve our understanding of key natural and anthropogenic land processes and boundarylayer feedbacks. The study area is in the Ebro basin of northeastern Spain in a hot, dry Mediterranean climate,with a sharp demarcation between a vast intensively irrigated region and a much drier rainfed zone to the east.Analysis of the observations reveal strong surface heterogeneities of evapotranspiration within the irrigatedzone (differences upwards of approximately 7 mm day-1 between fields), linked to the crop type, vegetationphenology and soil moisture, all of which were modulated by irrigation. The significant surface flux differencesbetween the irrigated and rainfed zones were found to result in strongly contrasting atmospheric boundarylayer properties (between 2 supersites separated by 14 km) extending upwards through the lowest several kmof the atmosphere
Discovery of ionized circumstellar gas emission around the long-period Cepheid Carinae with ALMA
No full textInternational audienceCepheid circumstellar emissions have previously been detected via both infrared excess and infrared interferometric observations at a few stellar radii. Those studies have shown that these circumstellar emission can be produced by ionized gas, however there is no direct observational evidence to confirm this hypothesis. In this letter we explore the continuum emission and a spectrum of the bright and long-period Cepheid, ~Car (day) at millimeter-wavelengths in order to detect possible effects of ionized gas emission. We presented ALMA observations of Car in two spectral setups in Band~6 (near 212 and 253\,GHz, respectively) and we compared the measured flux density to one expected for the stellar continuum. We also derived the spectral index and probed the presence of Radio Recombination Lines (RRL). We report statistically significant emission of about 3.5mJy in the two spectral ranges, which is about 2.5 times the stellar continuum emission. For the first time, we are also able to derive the spectral index of the flux density (), 0.44 (3 error), which is characteristic of partially optically thick ionized gas emission. Additionally, we discovered an emission line from a RRL of hydrogen H29 centered on the stellar rest velocity, smaller in spatial extent than about 0\farcs2 (AU), with a symmetric profile with a width at half power of 55.37.5\,\kms (1 error). It confirms the presence of ionized gas emission near ~Car. The millimeter emission detected from Car can be attributed to ionized gas emission from the Cepheid's chromosphere. Further radio interferometric observations are necessary to confirm the occurrence of these ionized gas envelopes around Cepheids of different pulsation periods
Probing Deeper into the Milky Way for Pulsars
No full textInternational audienceThis is the News and Views for the FAST Galactic Plane Pulsar Snapshot survey VI by Han et al. (, https://doi.org/10.1088/1674-4527/ada3b7) in this issue